dephlogisticated air UK /diːflə(ʊ)ˌd͡ʒɪstɪkeɪtid ˈɛə/US /difləˌd͡ʒɪstəˌkeɪtid ˈɛɚ/ noun1 •(historical) oxygen gas, as originally thought to be air deprived of phlogiston (“the hypothetical fiery principle formerly assumed to be a necessary constituent of combustible bodies and to be given up by them in burning”).[Joseph] Priestley never swayed from his firm conviction in the phlogiston theory as long as he lived, and he called his new gas ‘dephlogisticated air’. — 2002
